Anti-slide splice welder

ABSTRACT

An ultrasonic welder for splicing a plurality of workpieces has four anvils, each formed with a meeting surface and displaceable to form a workpiece nest, which has a rectangular shape of a predetermined width. The width of the workpiece nest is sufficient to receive only at least one vertical column of workpieces to be welded, so as to produce a vertical splice. The ultrasonic welder further has a controller controlling a starting position of tooling, which forms the predetermined width of the workpiece nest, and displacing at least one of tools, which form side faces of the nest in reciprocal and time controlled manner. The displaceable tool is brought back to its starting position corresponding to the predetermined width of the workpiece nest before a new bundle of workpieces is loaded therein.

FIELD OF THE INVENTION

This invention relates to an ultrasonic welding apparatus and a methodof operating the same. Particularly, the invention relates to anultrasonic apparatus including a plurality of anvils displaceablecontrollably to produce a desirable cross-section to allow electricalconductors to be welded substantially in at least one column andautomatically formed before each welding operation. The inventionrelates a method for sequentially displacing a plurality of anvils toproduce the desirable cross section to obtain a weld including at leastone column of welded conductors.

BACKGROUND OF THE INVENTION

Use of devices adapted to ultrasonically weld electric conductors,preferably in stranded form, has become a preferable method of weldingin electronic industry. An ultrasonic welder is typically provided witha welding tip which produces ultrasonic vibration and an anvil as amating tool. The anvil includes a plurality of faces, each movable alonga linear path to define a space in which the conductors can becompressed to varying dimensions while ultrasonic vibration is beingapplied to them. When the anvil is closed and the conductors are beingcompressed to one another, the anvil faces form a peripherally closedcompartment. When the anvil is open, the end faces are left open for theconductors to pass through it.

A device of this type is known from U.S. Pat. No. 4,867,370 to Welter etal. (Welter '370), where provision is made for variously dimensionedwires which are to be welded while maintaining a tight grip around theconductors.

FIGS. 1-4 of this application illustrate a mode of operation of Welter'370 that starts with having a wide open working area 4 receiving abundle of wires 2 loosely inserted in this area. Upon positioning thewires in an arbitrary manner, components forming the working area moveinwardly to tightly enclose the wires to be welded. As is disclosed inWelter '370, displacement of the components is a function of thefineness of wire ends and is sequenced to move a gathering block 6following moving of anvil 16 and welding tip 8 to reduce the workingarea, as illustrated in FIGS. 1-3. Finally, as shown in FIG. 4,subsequent to the welding of the wires, the gathering tool moves awayfrom the working area beyond its initial position, and then it isdisplaced back to its initial position.

It has been found that there is a greater efficiency of welding wiresthat are vertically stacked between a vibrating horn and stationaryanvil, as compared to those wires that are adjacent to each other. Theabove discussed reference is representative of the state of art anddiscloses a multiplicity of wires many of which are positioned adjacentto each other along a welding surface of the tip. Others, however,although welded in a vertical plane tend to fill interstices betweensubsequent wires of the adjacent column and welded diagonally therewithwhich produces a relatively inefficient weld. As a consequence, somewelds are weaker than others based on the way the wires have beenloaded.

It is, therefore, desirable to provide an ultrasonic welding apparatusfor wire splicing which automatically sets the position of the toolingso as to restrict a wire nest and require the operator to stack thewires in at least one vertical row extending from a welding tip. It isalso desirable to provide a method of operating the ultrasonic apparatusand allowing the tooling to move away from the wire nest for apredetermined period of time, and subsequently to move back in aninitial position characterized by a preset width.

SUMMARY OF THE INVENTION

This is obtained by a welding apparatus in accordance with the inventionthat automatically sets the position of the tooling so as to restrict awire nest and require an operator to vertically stack the wires, thusassuring the highest quality weld.

In accordance with one aspect of the invention, the welding apparatus isprovided with a memory unit containing a table of desirable dimensionsof the wire nest in accordance with type and cross-section of the wiresto be welded.

Still, further, the memory can contain a table of desirable pressureswhich is preferably inserted by an anvil upon a stack of wires placed inthe pre-set wire nest in accordance with the type and approximatequantity of the wires to be welded.

According to another aspect of the invention, a gathering toolconstituting one of the anvil surfaces, which form a wire nest of theultrasonic apparatus, automatically reciprocally moves away from andback to an initial position corresponding to the preset dimension of thewire nest. The displacement of the gathering tool is arrested for apreset period of time before moving back to the initial position toallow the operator to safely remove the splice.

In accordance with still a further aspect of the invention, a method ofoperating the apparatus is disclosed.

It is an object of the invention to provide a welding apparatuspreventing side splices in order to improve splice quality.

Still another object of the invention is to provide a welding apparatusautomatically setting a desirable dimension of a wire nest before aplurality of wires to be welded are placed in the nest, so as to providea vertical stack of wires between the vibrating horn and stationaryanvil.

A further object of the invention is to provide a plurality of wires tobe welded with a desirable pressure sufficient to efficiently weld astack of wires in accordance with the number and size of the wires to bespliced and with pre-set dimensions of the wire nest.

Another object of the invention is to provide a method of operating theultrasonic apparatus in accordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages will become morereadily apparent from the description of the preferred embodiment of theinvention accompanied by the following drawings, in which:

FIGS. 1-4 a front view in elevation, partly in cross-section, of anultrasonic welding apparatus illustrated at different stages of atypical method of operation of the apparatus in accordance with theknown prior art.

FIGS. 5 is a front view in elevation, partly in cross-section, of awelding apparatus at a stage wherein a plurality of wires is loaded in apreset wire nest.

FIG. 6 is a view similar to the one shown in FIG. 5 and illustrating asubsequent stage wherein the wire nest is enclosed.

FIG. 7 is a view similar to the one shown in FIG. 6 and illustrating astage at which the wire nest has a reduced cross section upon displacinga surface, which exerts a predetermined pressure upon a stack of wires.

FIG. 8 is a view similar to the previous views and illustrating thewelding apparatus in accordance with the invention at a stage of formingthe splice.

FIG. 9 is a view illustrating the welding apparatus in accordance withthe invention at a stage of removing the splice.

FIG. 10 is a view similar to the one shown in FIG. 4 and illustrating astage an initial stage wherein a pre-set dimension of the wire nest isautomatically established.

FIG. 11 is a view similar to the previous views and illustrating a stageof loading the wires in the preset wire nest.

FIG. 12 is a top, partially broken away view of a vibrating hornprovided with a welding tip in accordance with the invention.

FIG. 13 is a perspective view of a welding tip.

FIG. 14 is a cross sectional view of the welding tip along lines XIV—XIVseen in FIG. 13.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 5-11 a welding apparatus 10 in accordance with theinvention includes a tip guide 12 a vertical position of which withrespect to a welding tip 18 may be adjusted by an actuator 14 shown onlydiagrammatically. The tip 18 removably attached to an ultrasonic weldinghorn 22 serves as a reference surface for the entire structure, and isjuxtaposed with the tip guide 12 to arrest the tip guide's displacementin a predetermined position. The tip 18 is preferably square in crosssection, as better illustrated and explained in FIGS. 12-14 and may havea plurality of workfaces 20 receiving wires 24 to be spliced. Theworkfaces, each adjacent a respective corner, can be serrated forfacilitating loading of the wires 24.

Mounted on the tip guide 12 is an anvil 26 displaceable laterally andparallel to the tip guide 12 in a direction of arrow A by an actuator28, which is preferably an air piston and cylinder unit. Completing acombination of displaceable elements of the present invention is agathering tool 30 movable parallel to the anvil and tip guide uponactuation of a mother screw 32. All of the elements are automaticallydisplaceable relative to one another to form a wire nest 34, as isexplained herein below.

Referring specifically to FIGS. 5 and 11, an operator using a scrolldown menu 36 introduces a data including a type of an individualworkpiece, which data is inputted in a CPU 38 typically having a memory40 which contains a size of the introduced type. Additionally, anoperator introduces a size of the entire bundle of workpieces inaccordance with the operator's knowledge and experience based on thefact that the electrical wires to be welded have the precise size. As aresult, the movable anvil surfaces are actuated in a predeterminedsequence, as explained hereinbelow, to form a preset width of the wirenest as per memory 40 sufficient to form a predetermined width of thewire nest. Particularly, this width W=DN, wherein D is a diameter ofsingle wire or workpiece, and N is a number of columns. As will beexplained below, this width is sufficient only to place the wires in aseries of adjacent vertical columns to achieve a high quality weld.

Initially, as shown in FIG. 11, the welding tip 18 and tip guide 12 aredisplaceable to either have their meeting surfaces 42, 44, respectively,stopped at a very small distance, such as at most 0.002 inches, fromeach other or contacted each other. It is desirable to avoid africtional load between movable parts of the apparatus during presettingthe wire nest. However, once the predetermined width is set, the partsmay move further to close up the distance therebetween so as to ensurethat none of the wires, subsequently loaded in the wire nest, is caughtbetween the parts during welding.

Subsequently, the gathering block is actuated to move towards thesurface 44 of the tip guide 12. Since the CPU 38 automatically controlsthe displacement by, for instance, controlling a number of turns of thescrew 32 per time unit, the gathering block comes to a stop at apredetermined distance from the surface 44. Typically, this distancecorresponds to a desirable width of the wire nest sufficient forstacking the wires in at least one column extending vertically from thewelding tip. The displacement of the gathering block is arrested once itreaches a predetermined position corresponding to a desirable width ofthe work nest.

Alternatively, the sequence of controllably displacing the tip guide 12and the gathering block 30 can be reversed by first moving the gatheringblock at a predetermined distance, and only then, displacing the tipguide to form the preset width of the wire nest in response to theintroduced data. Further, it is possible to simultaneously displace thegathering block and tip guide to obtain the preset width in accordanceto the introduced data.

Regardless of the sequence leading to the preset width of the wire nest,only after it has been thus obtained, an operator loads wires 24 thatcan be positioned there only in a vertical plane, as shown in FIG. 5.If, however, the number of wires are great, then the width of the wirenest is set to be W=DN, as explained above. In this case, the width ispreset to provide a space sufficient only for a limited number ofcolumns, each extending in a vertical plane which is parallel to theothers. In other words, there is no room between adjacent columnssufficient for the wires constituting one of the columns to getvertically misaligned and shift between two adjacent columns. Having thewires to be spliced stacked in parallel columns not only prevent spayingand plastic extrusion during the welding process, but such arrangementalso assures a high quality bond between the welded wires.

In the next stage of operation, as shown in FIG. 6, the anvil 26controllably moves towards the gathering block upon the actuation of theair piston and cylinder unit 28 to stop at a small distance from asurface 50 of the gathering block. An amount of air pressure stored inthe memory 40 of the CPU 38 may control the displacement of the anvil.Similarly to the controllable displacement of the gathering block, inaddition to the controllable air pressure, a sensor 46 may be installedto signal the end of the travel. As a result of such displacement, thewire nest containing at least one vertical column of the wires to bespliced is fully enclosed by surfaces 50, 52, 20 and 44 of the gatheringblock, anvil, tip guide and the welding tip, respectively.

Subsequent to forming the wire nest, as shown in FIG. 7, the anvil 26and the tip guide 12 move vertically downward, as indicated by arrow C,to reduce the size of the wire nest. This displacement is controlled bythe CPU 38 to exert a predetermined pressure, as is stored in the memory40, upon the stack of wires. Additional pressure sensors 54 showndiagrammatically and connected to the CPU 38 control the exertedpressure so it would be within a desirable range providing a highefficiency weld.

After the wire nest has been formed in accordance with the sequencedescribed above, welding of the wire ends 24 is effected by theultrasonic horn 22 vibrating the welding tip 18 parallel to thelongitudinal axis of the wires and perpendicular to displacement of thetooling along arrow A. Preferably the welding tip is oscillated at afrequency of 20-40 kHz.

As a result of welding, the wires as shown in FIG. 8 are spliced andposses hydraulic pressure so to remove the spliced wires from the wirenest the gathering block, anvil and tip guide are retreated to aposition shown in FIG. 9. After a predetermined period of timecontrolled by the CPU and sufficient for an operator to remove a slice46 (FIG. 10), the gathering tool is displaced back to stop at thepredetermined distance from the tip guide, as shown in FIG. 5. Thisperiod can last up to 5 seconds which allows the operator to remove theslice and his/her hands before the gathering tool moves back to theinitial position defining a predetermined width of the wire nest, asillustrated in FIG. 11. The gathering block and the anvil may startmoving away from the wire nest either simultaneously or, preferably,sequentially by first retreating of the gathering bock, and then movingthe anvil 26 away from the nest.

During repeated use of ultrasonic welding process, both the horn 22 andthe tip 18, as shown in FIGS. 12-14 are exposed to substantial wear as aresult of the ultrasonic vibration which generates a substantial amountof heat leading to premature failures of the tip and horn. To overcomethis problem, the tip 20 has a pair of spaced apart holes 60, each ofwhich has a continuous concentric pad 62, better seen in FIG. 14, thatreceives a respective bolt 64 fastening the tip 18 to an end face of thehorn 22. As a consequence, focusing the ultrasonic vibration in a closeproximity to the bolt holes 60 by efficiently transmitting ultrasonicvibration through the pads 62 kept intact with the horn by means of theconcentrated clamping force of the bolts. The extended surfaces of thetip provided with work surfaces 20 are free to vibrate without harm tothe horn or welding tip, which improves productivity and quality of theweld as well as durability of the vibrating parts of the apparatus.

As shown in FIG. 13, the welding tip has four serrated work surfaces(only tow are shown), three of which are auxiliary to form a new weldingsurface upon exhaustion of the previously used surface by simplyrotating the tip 18 around the horn 20.

Although the invention has been described with reference to a particulararrangements of parts, features and the like, these are not intended toexhaust all possible arrangements or features, and indeed many othermodifications and variations will be ascertainable to those of skill inthe art.

What is claimed is:
 1. A method of welding a plurality of workpieces,comprising the steps of: positioning a welding tip and a tip guideadjacent to one another; controllably advancing a gathering block towardthe tip guide to stop it in an initial position at a predetermineddistance from the tip guide, thereby establishing a preset width of apartly open workpiece nest; loading workpieces to be welded in the neston the ultrasonic tip, said preset width being selected so that theworkpieces are loaded in a vertical alignment with one another to format least one vertical column adjacent to the tip guide and the gatheringblock; controllably displacing an anvil downward toward the welding tipto peripherally close the workpiece nest, thereby exerting apredetermined pressure upon the column; ultrasonically agitating theworking tip to produce a splice; displacing the gathering block awayfrom the initial position to a rest position; resting said gatheringblock in the rest position for a predetermined period of time, therebyremoving the splice from the workpiece nest; and moving the gatheringblock back to the initial position, thereby establishing the presetwidth of the workpiece nest for receiving workpieces to be welded. 2.The method defined in claim 1, further comprising the step ofintroducing a data containing a diameter D of single workpiece and anapproximate number of the workpieces to be welded, the gathering blockbeing displaceable to form the preset width of the nest substantiallyequal to the diameter D times number of columns N in response to theintroduced data.
 3. The method defined in claim 2, further comprisingthe step of sensing contact between the one column and the gatheringblock and the tip guide upon loading of the workpieces to be welded inthe workpiece nest.
 4. The method defined in claim 1, further comprisingthe step of controllably displacing the anvil toward and away from thegathering block, thereby enclosing and opening the workpiece nest forsubsequent welding and removal of the splice.
 5. The method defined inclaim 4, further comprising the step of sensing the pressure exertedupon the one column by the anvil upon its displacement towards thewelding tip.
 6. The method defined in claim 1, further comprising thestep of delaying the displacement of the gathering block to the initialposition for a predetermined period of time.
 7. The method defined inclaim 6, wherein the predetermined period of time does not exceed 5seconds.
 8. The method defined in claim 1, further comprising the stepof simultaneously displacing the anvil and tip guide toward the weldingtip to controllably close the workpiece nest, the welding tip having awork surface extending generally in a horizontal plane and flanked byspaced apart side surfaces, one of which is adjacent to a meetingsurface of the tip guide extending vertically beyond the welding tip toform one of the walls of the workpiece nest.
 9. The method defined inclaim 8, wherein the working surface of the welding tip is serrated andis parallel to a bottom of the anvil formed with a serrated portionwhich faces the working surface of the welding tip upon enclosing theworkpiece nest.
 10. A method of ultrasonically welding workpieces,comprising the steps of: introducing a data corresponding to a diameterof a single workpiece to be welded with a plurality workpieces, eachhaving the diameter and collectively forming a bundle of predeterminedsize; forming a partially open workpiece nest by displacing gatheringblock and tip guide block linearly in opposite directions to form sidesurfaces of the workpiece nest; arresting the displacement of the tipguide and gathering blocks to obtain a predetermined width of theworkpiece nest corresponding to the predetermined size of the bundle ofworkpieces in response to the introduced data; loading a plurality ofworkpieces substantially aligned with one another in a vertical plane onthe welding tip in the workpiece nest, thereby forming at least onevertical column abutted by the side surfaces of the workpiece nest;controllably displacing an anvil toward the welding tip to exert apredetermined pressure upon the one column, thereby forming a splice;and reciprocally displacing at least one of the gathering and tip guideblocks away from the workpiece nest to provide a predetermined period oftime sufficient to remove the splice, and back to repeatedly provide thepredetermined width of the workpiece nest.